This invention relates generally to a method and apparatus for viewing and interacting with real world items such as a pointing wand, wherein the pointing orientation of the wand can be detected by a computer system from a video camera image of the object. More particularly, the object includes an alignment indicator representative of a pointing direction and at least three equidistantly spaced co-linear points whose inter-spacing distance is known. Observation of the object by the video camera, in combination with known camera geometric dimensions provides a basis for converting the projected two-dimensional image of the object into a three-dimensional coordinate definition of the object in a free space. The invention is particularly applicable to a processing system where a three-dimensional object such as a pointing wand is intended to be used as an interface for communicating data or instructions from a user to the system. However, it will be appreciated to those of ordinary skill in the art that the invention could be readily adapted for use in other environments as, for example, where three-dimensional imaging or display methods are advantageously employed for communication or other informational purposes.
The ubiquitous use of PC workstations and the fact that such workstations will increasingly include a video camera for data input and communication presents an opportunity for expanding the nature and forms of data input to the system and interface tools for implementation of such communication.
For many years now it has been possible to present three-dimensional views of computer generated images. This is done by presenting a different view to each eye of the viewer. One method of doing this is to alternate the two views in time on a CRT display while the viewer wears special LCD shutter glasses that synchronously hide one image or the other from the viewer's left and right eyes. Other methods such as head-mounted displays that present different views to each eye are also available. With the help of this display technology the user can see a three-dimensional virtual construction suspended before his or her eyes. However, one would also like to interact with such constructions, to point to locations on it or to add to it. For such interaction, a three-dimensional locating device would be most useful. Such a device can seemingly provide the computer with an indicated position in the three-dimensional space between the viewer and the system display.
A particular problem with interfacing with such a locating device is position and orientation identification of the device in three dimensions. A single camera will only have a two-dimensional view plane. A plurality of cameras can provide the necessary three-dimensional data input but relative camera position tuning, as well as the cost of providing more than a single camera, presents an incentive towards developing a single camera system.
The present invention contemplates an interaction tool for the three-dimensional representations of position and pointing orientation based on the captured image from a single video camera of a kind currently readily available in many present PC workstations.